Park rangers at Bernardo O'Higgins National Park said they found a 100-feet-deep crater in late May were the lake had been in March. Several large pieces of ice that used to float atop the water also were spotted.

"The lake had simply disappeared," Juan Jose Romero, head of Chile's National Forest Service in the southernmost region of Magallanes, said Wednesday. "No one knows what happened."

A group of geologists and other experts will be sent to the area 1,250 miles southeast of Santiago in the next few days to investigate, Romero said.

One theory is the water disappeared through cracks in the lake bottom into underground fissures. But experts do not know why the cracks would have appeared because there have been no earthquakes reported in the area recently, Romero said.